The present invention relates generally to optical scanners and, more particularly, to color optical scanners of the type employing a light beam color separator, or "beam splitter."
Optical imaging devices which utilize a chromatic beam splitter consisting of composited dichroic beam splitter plates which separate a light beam into parallel color component beams are disclosed in U.S. Pat. No. 4,709,144 of Kent J. Vincent and U.S. patent application Ser. Nos. 145,174 and 333,850, filed Jan. 19, 1988, and Apr. 4, 1989, respectively, of Kent J. Vincent and Hans D. Neuman, which are all hereby specifically incorporated by reference for all that is disclosed therein.
These reference disclose the use of a slit aperture to define an imaging light beam which is projected from a linear object. The imaging light beam is separated into multiple, spaced-apart, parallel component line images of different colors by the chromatic beam splitter. Each color component line image is projected onto an associated linear photodiode array. Each of the linear photodiode arrays lie in a common plane and are separated by a distance proportionate to the thickness of the individual composite glass plates of the beam splitter.
Applicant has discovered, in certain applications of the color imaging assembly disclosed in U.S. Pat. No. 4,709,144 and patent application Ser. Nos. 145,174 and 333,850, that problems arise with respect to the registration of the color component line images with the associated linear photodiode arrays. Applicant has also discovered that the beam splitter described in the above-listed references produces secondary, off-color component images which are positioned between primary color component images. The existence of these secondary component images further complicates the previously-mentioned registration problem.